FACULTY OF APPLIED SCIENCESB. Sc. (Hons.) ENVIRONMENTAL TECHNOLOGY

EVT 577 : WASTEWATER TECHNOLOGY

LAB NO : 3

TITLE : BIOCHEMICAL OXYGEN DEMANDS (BOD)

GROUP : AS2294A

GRADER : NURUL NADIAH MOHD FIRDAUS

DATE OF EXPERIMENT

: 24 MARCH 2016

NAME / STUDENT ID : 1) MUHAMAD FADZRIL BIN AFINDI2014860708

2) FAIZAL BIN ALIAS2014225942

3) MOHD FAHMI BIN MOHD YUSOF 2014415098

3INTRODUCTION

BOD is defined as the amount of oxygen required by living organisms in the stabilization of the organic matter of water. If the oxidation of an organic compound is carried out by microorganisms using the organic matter as a food source, the oxygen is consumed. The greater the amount of organic matter present, the greater the amount of oxygen utilized. The BOD test is indirect measurement of organic matter. Since the test is performed over a five day period, it is often refferred as five day BOD (BOD5).

It is generally assumed that the rate at which oxygen is consumed directly proportional to the concentration of degradable organic matter remaining at any time. Different result would be obtained at different temperatures because biochemical reaction rates are temperature-dependent.

For five day BOD (BOD5), the sample is kept in incubator which remains around 20℃. Most of the biological process speed up as the temperature increase and slow down as the temperature drop. The temperature of 20℃ is standard temperature in lab and it is suitable for the bacteria active in breaking down the waste.

OBJECTIVES

To determine the Biochemical Oxygen Demand (BOD) in a water sample.

METHOD

1. Wastewater was diluted into 300 ml of deionised water and 300 ml of wastewater. The dilution factor is 0.5.

2. 2 Schott bottles was prepared where one bottles for DO1 and one bottles for DO5.3. The bottles was filled up with the diluted water. For DO5, the bottles was wrapped

instantly with foil and stored.4. 1 ml of MnSO4 and 1 ml of alkali-iodide-acids was pipetted into the DO1 bottle.5. A yellowish brown suspension reactions was formed. 1 ml of H2SO4 was added to the

suspension solution.6. The bottle was inverted until the suspension dissapeared.7. 200 ml of the solution was poured into a conical flask.8. 3-4 drops of starch indicator was added.9. The solution was titrated with sodium thiosulfate until the color changes from blue to

clear.10. Result was recorded for DO1.11. For DO5, steps 1-10 was repeated on day 5.

RESULTS AND CALCULATIONS

Result of the sample wastewater

pH : 6.71

BOD data table.

Sample of wastewater

READING (ml)DO1 8.20DO5 5.20

Dilution factor, n = 0.5

Calculation of the BOD

BOD5, mg/L = 8.20ml−5.20ml

0.5 = 6 ppm

DISCUSSIONS

BOD = DO1 – DO5

n

From the experiment, the samples that containing cautic alkalinity or acidity be must be adjusted before preparing BOD dilution. To conduct BOD experiment, the BOD dilution must be natural which range between pH values of 6.5 to 7.5 because microbes are most active in this range of pH value. The sample must be prepared not more than 24 hours. If it is begin within 2 hours of collection, cold storage is unnecessary but, if the test will begin within more than 2 hours, the sample must keep at or below 4⁰C during compositing.

The function of BOD bottle’s cap and seal water is to ensure that there is no air bubble is trapped in the bottle that will affect the characteristics of sample. It is also to prevent further oxygen dissolving in. Otherwise, bottle’s cap was using to reduce evaporation of the water seal during evaporation. The samples that containing residual chlorine can be dechlorinated before preparation of BOD dilutions because to determine valuable of bacterial source. Chlorine can kill the microbes live and bacteria in samples.

The samples which have been dechlorinated must be seeded with 300mL of BOD water in the BOD bottle before allows it store in the BOD incubator. DO levels are highest if the sample of water is not polluted means there is no toxic and bacterial effect so in sample of water there is a lot of oxygen demanding wastes is well within self-purification capacity. Otherwise, the BOD will low which is water sample not have microbes live. Then DO levels low if sample water not have enough oxygen to dissolve in water that need to all leaving things.

The BOD result is not in the range of Standard A and Standard B. Standard A (20mg/l) is the indicator for drinking water while Standard B (50 mg/l) is the indicator for inland water quality. Hence, we can say that the water sample is quite polluted. The organic material will consume the oxygen in the water due to the microbes’ activities. The consequence is the water polluted and the BOD5 reading is not in the range of standard water quality.

CONCLUSIONS

The Biochemical Oxygen Demand (BOD) has been determined. The water sample has been polluted as the BOD5 reading is out of the Standard A and B. The recommendation to solve the problem is to apply water treatment to the water source and to prevent incorrect handling of human activities that causes the pollution of water source.

REFERENCES

1. http://www.aboutcivil.org/To-Determine-Biochemical-Oxygen%20Demand-Of-A-Given-Sample.html

2. http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Environmental/BOD/coda.htm3. http://www.mantech-inc.com/products/why_bod_cod/

QUESTIONS

a) What is seeding process in BOD measurement?

Seeding is a process of adding live bacteria and microorganism to a sample. If the samples tested contain materials which could kill or injure the microorganisms, the condition must be corrected and healthy active organisms added.

b) Explain preparation of seed material.

Select a material to be used for seeding which will have a BOD of at least 180 mg/L. This will help ensure that the seed correction meets the 0.6 mg/L minimum specified in “Standard Methods”.

Place the material in a suitable container and incubate at 20°C for 24-36 hours. Usually, settled raw domestic sewage prepared in the manner above will have sufficient BOD for use as a seed material. If not, small quantities of digester supernatant, return activated sludge, or an acclimated seed material can be used to increase the potency of the seed material used for the test.

As an alternative, commercially available seed material may be used. The seed correction should not exceed 1.0 mg/L BOD; therefore, care should be taken not to use too strong a seed material for the test.

The key to a good seed correction is a relatively stable seed material which produces a good seed correction in every test situation

c) What materials can be used to seed a BOD sample?

Any source of water which can provide a suitable population of organisms can be used, however, settled raw sewage or commercially prepared seed material are the most common sources.

d) What is the significance of dissolved oxygen?

Dissolved oxygen allows animals to breathe in water and it provides a suitable habitat for the other animals. Bacteria in the water also use this oxygen to break down animals and plants. The oxygen level is not very high in most water sources. If the oxygen level is reduced, the animals begin to die. It is also to maintaining the aquatic life and aesthetic quality of streams and lakes.